The funny zebra-like patterns shown in this figure emerge
when a mixture of large - rough and small - smooth particles
are poured on a heap.
With Yan Grasselli we measured the dependence of the
wavelength on filling rate, cell geometrie and particle size.
This was published in
Granular Matter Vol.1, p.43-47 (1998).
Hernan Makse we made a model of particles jumping
down a heap surface which reproduced the observed
segregation patterns including the above strata as seen in the
figure left. More can be found in the
paper published in Europhys. Lett., Vol. 43, p. 1-6 (1998).